Very low frequency or VLF has a generally accepted definition of radio frequencies (RF) in the range of 3 kHz to 30 kHz and whereas Extremely low frequency (ELF) has a generally accepted definition of electromagnetic radiation with frequencies from 3 Hz to 3 KHz.
Due to the the difficulty of fabricating antennas configured to radiate the long waves of the VLF and ELF bands, such antennas have been used in relatively few communication systems. While these bands are capable of modulation some extremely low bitrate data, they have found usefulness in penetrating sea water and rock, and enable Subterranean or sub oceanic radio communications.
Conventional means of transmitting in these bands necessitate the use of long power lines, or earthed dipoles, as leads. These leads could be on the order of several kilometers long. Due to the inefficiency of this method, considerable amounts of electrical power are required to energize the antenna.
An additional use for ELF/VLF transmission systems is related to protecting space-based electronic assets from damaging energic radiation particles. Injection of whistler mode waves, the non electrostatic component of a generated ELF wave spectrum, into the ionosphere is effective at reducing the MeV fluxes of damaging energetic particles. Unfortunately, current antenna geometries produce only a weak whistler mode component as a function of total power consumption (low efficiency), and those known configurations are impractical for space deployment.
As a result, there exists a need in the art for a compact, high efficiency, ELF/VLF antenna apparatus and related methods for mitigating damaging energetic particles.